From: Ian Kent <raven@themaw.net>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
autofs mailing list <autofs@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Omar Sandoval <osandov@osandov.com>
Subject: Re: [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks
Date: Thu, 27 Oct 2016 10:51:40 +0800 [thread overview]
Message-ID: <1477536700.2898.16.camel@themaw.net> (raw)
In-Reply-To: <20161027021753.GJ19539@ZenIV.linux.org.uk>
On Thu, 2016-10-27 at 03:17 +0100, Al Viro wrote:
> On Tue, Oct 11, 2016 at 01:34:18PM +0800, Ian Kent wrote:
> >
> > + path = file->f_path;
> > +
> > /*
> > * An empty directory in an autofs file system is always a
> > * mount point. The daemon must have failed to mount this
> > @@ -123,7 +126,7 @@ static int autofs4_dir_open(struct inode *inode, struct
> > file *file)
> > * it.
> > */
> > spin_lock(&sbi->lookup_lock);
> > - if (!d_mountpoint(dentry) && simple_empty(dentry)) {
> > + if (!path_is_mountpoint(&path) && simple_empty(dentry)) {
> Why not &file->f_path, provided that you constify that thing properly?
Yep, my bad, as pointed out by Eric.
Patches to fix that and constify a bunch of things will follow.
>
> >
> > + if (rcu_walk) {
> > + if (!path_is_mountpoint_rcu(path))
> > + return -EISDIR;
> > + } else {
> > + if (!path_is_mountpoint(path))
> > + return -EISDIR;
> IDGI. What's the point of _having_ the _rcu() variant, anyway? Here you
> are probably paying more in terms of i-cache footprint/branch prediction
> than you win on not doing that rcu_read_lock()/rcu_read_unlock()...
>
> _rcu variants make sense when non-RCU case does something you can't do
> under RCU; here your path_is_mountpoint() is pretty close to being
> rcu_read_lock()+path_is_mountpoint_rcu()+rcu_read_unlock() anyway...
Again, my bad, I'll merge these two and post along with the follow up patches
above.
Thanks Al,
Ian
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next prev parent reply other threads:[~2016-10-27 2:51 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 5:33 [PATCH 1/8] vfs - change d_manage() to take a struct path Ian Kent
2016-10-11 5:33 ` [PATCH 2/8] vfs - add path_is_mountpoint() helper Ian Kent
2016-10-11 5:34 ` [PATCH 3/8] vfs - add path_has_submounts() Ian Kent
2016-10-11 5:34 ` [PATCH 4/8] autofs - change autofs4_expire_wait() to take struct path Ian Kent
2016-10-11 5:34 ` [PATCH 5/8] autofs - change autofs4_wait() " Ian Kent
2016-10-11 5:34 ` [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks Ian Kent
2016-10-27 2:17 ` Al Viro
2016-10-27 2:51 ` Ian Kent [this message]
2016-10-11 5:34 ` [PATCH 7/8] autofs - use path_has_submounts() to fix unreliable have_submount() checks Ian Kent
2016-10-11 5:34 ` [PATCH 8/8] vfs - remove unused have_submounts() function Ian Kent
2016-10-11 16:04 ` [PATCH 1/8] vfs - change d_manage() to take a struct path Eric W. Biederman
2016-10-11 23:47 ` Ian Kent
2016-10-19 19:40 ` Andrew Morton
2016-10-20 23:39 ` Ian Kent
2016-10-27 2:11 ` Al Viro
2016-10-27 2:47 ` Ian Kent
2016-10-27 6:50 ` Ian Kent
2016-11-01 2:02 ` Ian Kent
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